Lambert-Eaton myasthenic syndrome

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Lambert-Eaton myasthenic syndrome



Lambert-Eaton myasthenic syndrome


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Lambert-Eaton myasthenic syndrome

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USMLE® Step 1 style questions USMLE

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A 65-year-old man comes to his outpatient provider because of a chronic cough for the past 3 months. It is occasionally accompanied by flecks of blood-tinged sputum. Review of systems is significant for weakness in the hips and thighs bilaterally and 15 lbs (6.8 kg) weight loss. Past medical history is notable for hypertension. He only takes hydrochlorothiazide. Social history is notable for a 50-pack-year smoking history. In the office, his temperature is 37.0°C (98.6°F), pulse is 76/min and blood pressure is 157/85 mmHg. Pulmonary examination reveals expiratory wheezing on the left side in 5th intercostal space. A chest radiograph is ordered and reveals the following:

Reproduced from:   

Laboratory testing reveals a creatinine kinase level of 75 U/L. Which of the following additional examination findings will most likely be present in this patient?  

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Calcium channels

Lambert-Eaton myasthenic syndrome p. 221

Dry mouth

Lambert-Eaton myasthenic syndrome p. 484

Erectile dysfunction p. 590

Lambert-Eaton myasthenic syndrome p. 483

Lambert-Eaton myasthenic syndrome p. 484

autoantibody p. 113

as paraneoplastic syndrome p. 221

small cell lung cancer p. 709

Sexual dysfunction p. 590

Lambert-Eaton myasthenic syndrome p. 483

Small cell lung cancer p. 732

Lambert-Eaton myasthenic syndrome p. 484

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In Lambert-Eaton myasthenic syndrome, myasthenia refers to muscle weakness, and Lambert-Eaton refers to Edward Lambert and Lealdes Eaton, the two physicians who first described the condition.

Lambert-Eaton myasthenic syndrome is a rare autoimmune disease that attacks the peripheral nervous system, causing muscle weakness, and actually improves temporarily after repeated use of the muscle.

The nervous system is divided into the central nervous system, which is the brain and spinal cord, and the peripheral nervous system, which includes all the nerves that connect the central nervous system to the muscles and organs.

The peripheral nervous system can then further be divided into the somatic nervous system, which controls voluntary movement of our skeletal muscles, and the autonomic nervous system, which is even further divided into the sympathetic and the parasympathetic, and controls the involuntary movement of the smooth muscles and glands of our organs.

Now, to better understand Lambert-Eaton myasthenic syndrome, let’s review normal skeletal muscle contraction at the cellular level.

First you’ve got your motor neurons, which have voltage-gated calcium channels in their membranes.

Whenever a motor neuron receives an electrical impulse from the brain, these channels open up and let calcium inside.

The increased intracellular calcium concentration triggers the release of small vesicles that contain the neurotransmitter acetylcholine into the neuromuscular junction.

Acetylcholine goes from the neuron over to the nicotinic receptors on muscle cell membranes.


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  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  4. "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
  5. "Available treatment options for the management of Lambert-Eaton myasthenic syndrome" Expert Opinion on Pharmacotherapy (2006)
  6. "Available treatment options for the management of Lambert-Eaton myasthenic syndrome" Expert Opinion on Pharmacotherapy (2006)
  7. "Lambert-Eaton Myasthenic Syndrome" Seminars in Neurology (2004)

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